GB780646A - An improved method of superheating vapour and improvements in tubulous steam generating and superheating units - Google Patents

Abstract

780,646. Steam superheaters. BABCOCK & WILCOX, Ltd. March 14, 1956 [March 16, 1955], No. 7927/56. Class 123(3) A water-tube steam boiler comprises a cyclone furnace 10 of the form described in Specification 598,141 having a throat 24 in the front wall 26 of the unit, the wall 26 being lined with steam generating tubes 30 which are bent inwardly above the throat to form an arch 32 the nose of which has openings for recirculated flue gas formed by offsetting some of the tubes. Opposite the arch 32 the rear wall lining tubes 52 are bent to provide a similar arch 33 also having recirculated gas openings. Above the arches 32, 33 is a gas cooling chamber 130 from which a lateral pass locating secondary and primary superheaters 132, 134 extends to a gas turning space 140. From the latter a downpass 142 in which is disposed an economizer 144...146 conveys the furnace gases to an air heater 148, 154. To enable high superheat temperatures to be attained when firing slagforming fuels, platens 72, 74, 76, 78 of refractory-covered, studded, superheater tubes are disposed to form the target wall of a secondary furnace 84, the gases from the furnace 10 carrying fused slag particles impinging on the wall, the molten slag collecting thereon running into a chamber 90 and thence into a slag pit 96. Behind the target wall similar refractory-covered superheater tube platens 100...103 extend at right angles, these platens being widelyspaced across the unit. Molten slag collecting on the platens 100...103 also runs into the pit 96. The gases leaving the radiantly-heated superheater platens are tempered by admixture with cool flue gas in the chamber 130 to solidify the slag particles remaining therein before the gases contact the superheaters 132, 134. Fouling of the tubes of the latter by sticky slag particles is thus avoided. Flue gas for recirculation is withdrawn from the bottom of the pass 142 by a fan 200 and delivered through damper-controlled ducting 208, 210, 214 to the openings in the arches 32, 33. The rate of gas recirculation may be varied to control the superheat temperature. Specification 526,825 also is referred to.